U.S. patent application number 14/116107 was filed with the patent office on 2014-03-13 for routing terminating call to user equipment via control nodes.
This patent application is currently assigned to Telefonaktiebolaget L M Ericsson (PUBL). The applicant listed for this patent is Fredrik Alriksson, Ralf Keller, Fredrik Lindholm, Karl-Perter Ranke. Invention is credited to Fredrik Alriksson, Ralf Keller, Fredrik Lindholm, Karl-Perter Ranke.
Application Number | 20140073333 14/116107 |
Document ID | / |
Family ID | 46017769 |
Filed Date | 2014-03-13 |
United States Patent
Application |
20140073333 |
Kind Code |
A1 |
Keller; Ralf ; et
al. |
March 13, 2014 |
ROUTING TERMINATING CALL TO USER EQUIPMENT VIA CONTROL NODES
Abstract
A method for routing a terminating call to a user equipment via
a first control node for controlling the call, wherein the user
equipment is attached to a second control node which is adapted to
provide routing information. The method comprises determining, by
the second control node, if the user equipment is attached to the
second control node over a third control node, wherein the
attachment over the third control node indicates that call control
shall be performed by a specific service domain. Based on the
determining, the provided routing information is selected by the
second control node, wherein the routing information indicates to
the first control node if the further call establishment to the
user equipment is controlled either by the second control node or
by the third control node. The call is then routed, by the first
control node, according to the selected routing information.
Inventors: |
Keller; Ralf; (Wurselen,
DE) ; Alriksson; Fredrik; (Sundbyberg, SE) ;
Lindholm; Fredrik; (Stockholm, SE) ; Ranke;
Karl-Perter; (Herzogenrath, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Keller; Ralf
Alriksson; Fredrik
Lindholm; Fredrik
Ranke; Karl-Perter |
Wurselen
Sundbyberg
Stockholm
Herzogenrath |
|
DE
SE
SE
DE |
|
|
Assignee: |
Telefonaktiebolaget L M Ericsson
(PUBL)
Stockholm
SE
|
Family ID: |
46017769 |
Appl. No.: |
14/116107 |
Filed: |
April 13, 2012 |
PCT Filed: |
April 13, 2012 |
PCT NO: |
PCT/EP2012/001612 |
371 Date: |
November 6, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61483203 |
May 6, 2011 |
|
|
|
Current U.S.
Class: |
455/445 |
Current CPC
Class: |
H04W 92/24 20130101;
H04W 76/10 20180201; H04L 45/306 20130101; H04W 40/02 20130101;
H04W 68/00 20130101 |
Class at
Publication: |
455/445 |
International
Class: |
H04W 40/02 20060101
H04W040/02 |
Claims
1. A method (500) for routing a terminating call (102) to a user
equipment (104) via a first control node (106) for controlling the
call (102), wherein the user equipment (104) is attached to a
second control node (108) which is adapted to provide routing
information, the method (500) comprising: determining (504), by the
second control node (108), if the user equipment (104) is attached
to the second control node (108) over a third control node (110),
wherein the attachment over the third control node (110) indicates
that call control shall be performed by a specific service domain
(112); based on the determining (504), selecting (506) the provided
routing information by the second control node (108), wherein the
routing information indicates to the first control node (106) if
the further call establishment to the user equipment (104) is
controlled either by the second control node (108) or by the third
control node (110); and routing (508), by the first control node
(106), the call (102) according to the selected routing
information.
2. The method (500) according to claim 1, wherein the attachment
over the third control node (110) indicates that the call control
shall be performed by an IP Multimedia Subsystem (112).
3. The method (500) according to claim 1 or 2, wherein the method
(500) comprises establishing the call (102) via at least one other
node being different from the control nodes (106, 108, 110), and
wherein the control nodes (106, 108, 110) only control the
establishment of a call leg.
4. The method (500) according to claim 3, wherein the method (500)
comprises involving the control nodes (106, 108, 110) in bearer
establishment for the call (102) only, while transporting payload
of the call (102) by at least one other node.
5. The method (500) according to any one of claims 1 to 4, wherein
the method (500) comprises indicating the attachment over the third
control node (110) by an association of the user equipment (104) to
an interface (114) between the second control node (108) and the
third control node (110).
6. The method (500) according to claim 5, wherein the interface
(114) between the second control node (108) and the third control
node (110) is an SGs interface.
7. The method (500) according to any one of claims 1 to 6, wherein
the method (500) comprises providing the routing information from
the second control node (108) to the first control node (106) via
one or via a plurality of subscriber registers.
8. The method (500) according to any one of claims 1 to 7, wherein
the determining (504) comprises a check if the user equipment (102)
is adapted to receive a call (102) under the control of the third
control node (110).
9. A second control node (108), comprising: an interface (302, 304)
to provide routing information; a processing system (306) adapted
to determine the association of a user equipment (104) to a third
control node (110) and for selecting the routing information based
on the determination.
10. The second control node (108) according to claim 9, adapted to
provide routing information which indicates that the user equipment
(104) is associated with the third control node (110).
11. A third control node (110), comprising: an interface (402, 404)
to provide information of a user equipment (104) attached to the
third control node (110) to a second control node (108); a
processing system (406) adapted to determine the association of the
user equipment (104) to the third control node (110) and
capabilities of the user equipment (104) to receive a call (102)
under the control of the third control node (110), and whether said
user equipment (104) is using or is adapted to use a specific
service domain (112).
12. The third control node (110) according to claim 11, wherein the
specific service domain (112) is an IP Multimedia Subsystem.
13. A communication system (100) for routing a terminating call
(102) to a user equipment (104), the communication system (100)
comprising: a first control node (106) via which the terminating
call (102) is routable to the user equipment (104) for controlling
the call (102); a second control node (108) to which the user
equipment (104) is attached and which is adapted to provide routing
information; wherein the second control node (108) is adapted to
determine if the user equipment (104) is attached to the second
control node (108) over a third control node (110), wherein the
attachment over the third control node (110) indicates that call
control shall be performed by a specific service domain (112);
wherein the second control node (108) is adapted to select, based
on the determination, the provided routing information, wherein the
routing information indicates to the first control node (106) if
the further call establishment to the user equipment (104) is
controlled either by the second control node (108) or by the third
control node (110); wherein the first control node (106) is adapted
to route the call (102) according to the selected routing
information.
14. The communication system (100) according to claim 13, further
comprising the third control node (110), wherein the third control
node (110) is adapted to: provide information of the user equipment
(104) attached to the third control node (110) to the second
control node (108), and determine the association of the user
equipment (104) to the third control node (110) and capabilities of
the user equipment (104) to receive the call (102) under the
control of the third control node (110), and whether said user
equipment (104) is using or is adapted to use the specific service
domain (112).
15. A data carrier (308, 408) comprising software, adapted to
execute the method (500) according to any one of claims 1 to 8 when
loaded into one or more processors (306, 406) of one or more
control nodes (108, 110).
Description
TECHNICAL FIELD
[0001] The invention relates to a method for routing a terminating
call to a user equipment via a control node for controlling the
call.
[0002] The invention also relates to control nodes for executing
such a method.
[0003] Beyond this, the invention relates to a communication system
for routing a terminating call to a user equipment.
[0004] Moreover, the invention relates to a data carrier comprising
software.
BACKGROUND
[0005] The 3GPP (3.sup.rd Generation Partnership Project) specified
IMS (IP Multi-media Subsystem) network is an access-independent and
standard-based IP connectivity and service control architecture
that enables various types of multimedia services to end-users
using common Internet-based protocols.
[0006] As outlined in 3GPP TS (Technical Specification by the
3.sup.rd Generation Partnership Project) 23.292, T-ADS
(Terminating-Access Domain Selection) shall be aware of currently
used access (PS, Packet Switched, or CS, Circuit Switched) to
forward terminating calls to a user. T-ADS shall also check for IMS
voice over PS support and RAT (Radio Access Type) type in the
serving MME (Mobile Management Entity) and/or SGSN (Serving GPRS
Support Node). T-ADS shall furthermore, for all terminating calls
for registered contacts (if registered via PS), query the current
serving nodes (via HSS, Home Subscriber Server) for IMS voice over
PS support and RAT type.
[0007] T-ADS obtains the aforementioned information (PS support and
RAT) via a reference point Sh from the HSS. HSS obtains the
information via reference points S6a to an EPC (Evolved Packet
Core) node MME or via Gr/S6d to SGSN.
[0008] Service Domain Selection (SDS) is a concept used to decide
on the serving domain for an originating call, for instance CS or
IMS, as described in 3GPP TS 23.221 as well as when a call arrives
at terminating GMSC (Gateway Mobile Switching Center) whether CS or
IMS network should serve the call as described in 3GPP TS
23.221.
[0009] 3GPP TS 23.292 describes a solution for a static domain
selection, i.e., originated and terminated calls are always routed
to the IMS.
[0010] SDS and T-ADS may also be considered in combination.
[0011] With introduction of IMS Centralized Services (ICS), user's
services are migrated from the CS network to IMS. IMS will be the
network serving the user as a single service engine meaning that
originating and terminating calls need to visit IMS.
[0012] It is assumed that ICS is introduced aligned with start of
VoLTE (Voice over LTE, i.e. Long Term Evolution) where MMTeI/IMS is
the recommended service engine.
SUMMARY
[0013] It is an object of the invention to improve the routing of
calls in a communication system with a plurality of service
domains.
[0014] In order to achieve the object defined above, a method for
routing a terminating call to a user equipment via a first control
node for controlling the call is provided, wherein the user
equipment is attached to a second control node which is adapted to
provide routing information. The method comprises determining, by
the second control node, if the user equipment is attached to the
second control node over a third control node, wherein the
attachment over the third control node indicates that call control
shall be performed by a specific service domain. Based on the
determination, the provided routing information is selected by the
second control node, wherein the routing information indicates to
the first control node if the further call establishment to the
user equipment is controlled either by the second or by the third
control node. The call is routed by the first control node
according to the selected routing information.
[0015] According to another embodiment of the invention, a second
control node is provided, particularly for contributing to
executing a method having the above mentioned features. The second
control node comprises an interface to provide routing information,
and a processing system adapted to determine the association of a
user equipment to a third control node and for selecting the
routing information based on the determination.
[0016] According to another embodiment of the invention, a third
control node is provided, particularly for contributing to
executing a method having the above mentioned features. The third
control node comprises an interface to provide information of a
user equipment attached to the third control node to a second
control node. The third control node further comprises a processing
system adapted to determine the association of the user equipment
to the third control node and capabilities of the user equipment to
receive a call under the control of the third control node, and
whether said user equipment is using or is adapted to use a
specific service domain.
[0017] According to still another embodiment of the invention, a
communication system for routing a terminating call to a user
equipment is provided. The communication system comprises a first
control node via which the terminating call is routable to the user
equipment for controlling the call. The communication system
further comprises a second control node to which the user equipment
is attached and which is adapted to provide routing information.
The second control node is adapted to determine if the user
equipment is attached to the second control node over a third
control node, wherein the attachment over the third control node
indicates that call control shall be performed by a specific
service domain. The second control node is further adapted to
select, based on the determination, the provided routing
information. The routing information indicates to the first control
node if the further call establishment to the user equipment is
controlled either by the second or by the third control node. The
first control node is adapted to route the call according to the
selected routing information.
[0018] An embodiment of the invention may be embodied in software,
for instance on a data carrier, adapted to execute the above method
when loaded into at least one processor of at least one control
node. For instance, part of the software may be loaded into a
processor of the above-mentioned second control node, whereas
another part of the software may be loaded into a processor of the
above-mentioned third control node. These parts of the software and
the processors may cooperate to carry out the above mentioned
method in combination.
[0019] Particularly, one or more program elements (for instance a
software routine, in source code or in executable code) may be
provided, which, when being executed by one or more processors
(such as a microprocessor or a CPU), is or are adapted to control
or carry out the method having the above mentioned features.
[0020] It is noted that the numbering of the nodes (such as first
control node, second control node or third control node) does not
necessarily imply that nodes having smaller numbers must be
necessarily present as well when a node with a higher number is
mentioned. In contrast to this, the numbering is performed for the
mere sake to obtain a consistent and logic numbering of nodes in
the claims and/or in the description.
[0021] Exemplary embodiments of the invention allow that
terminating calls are flexibly routed via specific paths under the
control of a selectable one of control nodes, thereby reducing
delay and capacity requirements of a call management system.
Depending on an actually applicable service domain, call
establishment to user equipment can be controlled by a
correspondingly chosen control node.
[0022] The aspects defined above and further aspects of the
invention are apparent from the examples of embodiment to be
described hereinafter and are explained with reference to these
examples of embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Embodiments of the invention will be described in more
detail hereinafter with reference to examples but to which the
scope is not limited.
[0024] FIG. 1 illustrates a communication network coupling a first
control node, a second control node, a third control node, and a
user equipment in accordance with an exemplary embodiment of the
invention.
[0025] FIG. 2 illustrates a workflow for operating a communication
network in accordance with an exemplary embodiment of the
invention.
[0026] FIG. 3 illustrates the constitution of the second control
node of FIG. 1.
[0027] FIG. 4 illustrates the constitution of the third control
node of FIG. 1.
[0028] FIG. 5 illustrates a flowchart of a method of operating a
communication network according to an exemplary embodiment of the
invention.
DETAILED DESCRIPTION
[0029] In the context of this application, the term "node" may
particularly denote any communication device, for instance a
transmitter/receiver device (transceiver), which allows for an
exchange of communication messages and/or data packets with a
communication partner over a communication system or network. Such
a node may be a computer (such as a server or a client). It may be
a wired or wireless communication device. A node may have
processing resources, storage resources, and message
transmitting/receiving resources. A control node may be a node
which fulfils control tasks.
[0030] In the context of this application, the term "user
equipment" (UE) may particularly denote a mobile communication
device, a portable communication device, a mobile terminal, a
mobile phone, a data card, a Personal Digital Assistant, a personal
computer, a laptop, etc. Hence, portable or stationary
communication devices can be operated in accordance with the
disclosed architecture of exemplary embodiments.
[0031] An exemplary embodiment of the invention relates to a method
for routing a terminating call to a user equipment via a first
control node for controlling the call. The user equipment is
attached to a second control node which is adapted to provide
routing information.
[0032] The second control node determines if the user equipment is
attached to the second control node over a third control node. The
attachment over the third control node indicates that call control
shall be performed by a specific service domain, for instance by an
IP Multimedia Subsystem.
[0033] Based on the determination, the second control node selects
the provided routing information. The routing information indicates
to the first control node if the further call establishment to the
user equipment is controlled either by the second or by the third
control node. The first control node can thus route the call
accordingly.
[0034] In this way, the proposed method can reduce delay and
capacity requirements of a call management system such as an IMS
system.
[0035] For example in early steps of IMS and VoLTE deployments,
both VoLTE and CS access co-exists due to lack of full LTE
coverage. The users will be served by CS and LTE however still IMS
will be used as service engine. For these scenarios, calls
originated in CS access need conventionally to be routed to IMS as
well as for cases when terminating user is on CS access, terminated
calls will need to visit IMS network to execute terminating
services for the subscriber. If the majority of calls in the
network are between users over CS access, routing of calls always
to IMS might add some delay and requires sufficient capacity in the
IMS which is not desirable. This can be improved by the proposed
method.
[0036] As already mentioned, the routing information may indicate
to the first control node if the further call establishment to the
user equipment is controlled by the second or by the third control
node. Particularly, the routing information may indicate only where
to route the call. It is for instance not essential for the first
control node (such as a GMSC), whether this is CS or IMS. More
particularly, from the perspective of the first control node, it
may be sufficient that the routing information indicates where to
route the call.
[0037] In the following, further exemplary embodiments of the above
method will be explained. However, these embodiments also apply to
the second control node, the third control node, the communication
system and the data carrier.
[0038] It should be noted that the call itself needs not to be
established via the control nodes because they may only control the
establishment of a call leg, for instance they may be involved in
bearer establishment for the call only while the payload of the
call is transported by other nodes. Hence, the processing
capabilities and the resource requirements of the control nodes may
be moderate.
[0039] More specifically, an embodiment of the invention may be
implemented in an environment which uses SDS in MSC (Mobile
Switching Center) for IMS Voice users. Exemplary embodiments of the
invention allow that originated calls on a CS network are not
forced into IMS and terminating calls reaching operators GMSC are
not routed to IMS unless the user is operating on E-UTRAN (evolved
UMTS Terrestrial Radio Access Network, wherein UMTS means Universal
Mobile Telecommunications System) and is an IMS Voice user.
[0040] Such a concept may result in an improvement or even
optimization of call routing and reduction of call set-up delays in
early stages of VoLTE deployment. There is no need to perform SDS
in HLR (Home Location Register)/HSS(Home Subscriber Server).
Exemplary embodiments of the invention can also be easily
implemented in existing MSCs because functionality related to the
SGs interface can be reused for the purpose of embodiments of the
invention.
[0041] In an embodiment, the attachment over the third control node
indicates, e.g. to the second control node, that the call control
shall be performed by an
[0042] IP Multimedia Subsystem.
[0043] In an embodiment the attachment over the third control node
is indicated by an association of the user equipment to an
interface between the second and the third control node, for
example an SGs interface or any other appropriate kind of
interface. Such an interface analysis is a very simple criterion
for determining such an attachment. SGs is an interface between MME
and MSC server. It can be used for Mobility Management (MM) and
paging procedures.
[0044] In a further embodiment, the routing information can be
provided via one or via a plurality of subscriber registers from
the second control node to the first control node. However, in
alternative embodiments the routing information may be stored
elsewhere, for instance in a database assigned to the second
control node.
[0045] In a still further embodiment, the determination can
comprise a check, e.g. based on information stored in the
communication system, if the user equipment is adapted to receive a
call under the control of the third control node so as to determine
whether the third control node is indeed capable of controlling the
routing of such a call.
[0046] Embodiments of the invention can also be implemented in a
second control node. Such a second control node comprises an
interface to provide routing information. The second control node
comprises also a processing system adapted to determine the
association of a user equipment to a third control node and for
selecting the routing information based on the determination.
[0047] In the following, further exemplary embodiments of the
second control node will be explained. However, these embodiment
also apply to the method, the third control node, the communication
system and the data carrier.
[0048] In particular, the second control node can provide a routing
information which indicates that the user equipment is associated
with the third control node. Therefore, the second control node may
be the entity which defined which routing information is used for
routing the call.
[0049] The second control node can be adapted to any embodiment of
the method as described above.
[0050] A third control node may also be adapted to exemplary
embodiments of the invention. The third control node comprises an
interface to provide information of a user equipment attached to
the third control node to the second control node. The third
control node comprises also a processing system adapted to
determine the association of the user equipment to the third
control node and capabilities of the user equipment to receive a
call under the control of the third control node, and whether said
user equipment is using or adapted to use a specific service
domain.
[0051] In the following, further exemplary embodiments of the third
control node will be explained. However, these embodiments also
apply to the method, the second control node, the communication
system and the data carrier.
[0052] The specific service domain can be an IP Multimedia
Subsystem.
[0053] The third control node can be adapted to any embodiment of
the method as described above.
[0054] Exemplary embodiments are described below with specific
reference to a 3GPP communication system with an IMS network. In
this case it implements a dual service engine, wherein for an equal
sub-set of supplementary services both CS and IMS network may be
provisioned with necessary data and may be synchronized.
[0055] The terminal, when operating on LTE, may use SMSoSGs (SMS,
Short Message Service, over SGs) or CSFB (Circuit Switched Fall
Back). In the following, SMSoSGs is used to exemplify.
[0056] FIG. 1 illustrates a communication network 100 in accordance
with an exemplary embodiment of the invention. The communication
network 100 couples a first control node 106 (in this embodiment a
GMSC), a second control node 108 (in this embodiment an MSS MGCF,
Mobile Switching Centre Server/Media Gateway Control Function), a
third control node 110 (in this embodiment an MME), and a user
equipment 104 (in this embodiment a SR, Single Radio User
Equipment, alternatively a DR, Double Radio User Equipment).
[0057] In this communication network 100, a method for routing a
terminating call 102 (such as a video or voice call) to the mobile
user equipment 104 via the first control node 106 is carried out
for controlling this call 102. The user equipment 104 is attached
to the second control node 108 which is, in turn, adapted to
provide routing information.
[0058] The method comprises determining, by the second control node
108, if the user equipment 104 is attached to the second control
node 108 over the third control node 110. The attachment over the
third control node 110 indicates that call control shall be
performed by a specific service domain 112, in this example IMS.
Based on the determination, the second control node 108 selects the
provided routing information for correspondingly routing the call
102 over an appropriate path of the communication network 100. The
routing information indicates to the first control node 106 if the
further call establishment to the user equipment 104 is controlled
by the second control node 108 or by the third control node 110.
According to the method, the call 102 is then routed by the first
control node 106 according to the selected routing information. The
attachment over the third control node 110 indicates that the call
control shall be performed by an IP Multimedia Subsystem (see
reference numeral 112).
[0059] It should be said that the call 102 needs not necessarily be
established by the control nodes 108, 110 but may be established
via another node of the communication system 100. In such an
embodiment, the control nodes 108, 110 only control the
establishment of the call leg. It is further possible to involve
the control nodes 108, 110 in bearer establishment for the call 102
only, whereas a payload of the call 102 may be transported by one
or more other nodes of the communication system 100.
[0060] It is possible that the above-mentioned attachment is
indicated over the third control node 110 by an association of the
user equipment 104 to an interface 114 between the second control
node 108 and the third control node 110. This interface 114 between
the second control node 108 and the third control node 110 is an
SGs interface in the shown embodiment.
[0061] The method of operating the communication system 100,
particularly of managing transmission of the call 102, further
comprises providing the routing information from the second control
node 108 to the first control node 106 via a subscriber register.
The routing data may hence be stored in such a subscriber
register.
[0062] The determination comprises a check if the user equipment
102 is adapted to receive a call 102 under the control of the third
control node 110.
[0063] Further components are provided as well in the communication
system 100 as well, i.e. a HLR (Home Location Register) 120 and a
HSS/HLR (Home Subscriber Server /Home Location Register) 122
communicatively coupled therewith. HSS/HLR 122 is further coupled
to SGSN 124. HSS/HLR 122 is further coupled to an SCC AS (Service
Centralization and Continuity Application Server) 130. GMSC or
first control node 106 is further coupled to MGCF VIG (Media
Gateway Control Function Video Gateway) 132, which is in turn
coupled to S&P GW (S&P Gateway) 128. Various networks
contribute to the communication within the communication system
100, i.e. a GSM (Global System for Mobile Communications)/TD-SCDMA
(Time Division Synchronous Code Division Multiple Access) network
134 and an LTE network 136. Various interfaces or communication
channels 138, 140, 142, 144, 146, 148, 150 are shown as well.
[0064] For terminating calls 102 reaching GMSC or first control
node 106, the HLR will request a roaming number from the MSC Server
or second control node 108 serving the subscriber operating the
user equipment 104. The MSC Server or second control node 108 can
then make a decision whether to return an MSRN (Mobile Station
Roaming Number), and hence the call 102 will be routed to the MSC
Server or second control node 108, or an IMRN (IMS Routing number,
which can simply be a prefixed B number), and hence the call 102
will be routed to the IMS 112. This is depicted in FIG. 1. FIG. 1
shows the routing of a voice call (dotted bold line) and a video
call (continuous bold line) over the first control node 106, in the
example a GMSC, either under control of the second control node
(MSS MGCF) 108 or under control of the third control node (MME)
110. The third control node 110 or the second control node 108 is
indicated in the Initial Address Message IAM by an IMRN or an MSRN.
The second control node 108 selects either the IMRN or the MSRN in
response to a request from the HSS or HLR 122. FIG. 1 indicates
also different reference points between involved nodes. Radio
networks for connecting mobile user equipment 104 to the control
nodes 108, 110 are indicated by ellipses (see reference numerals
134, 136) and may comprise further elements which are well-known to
a skilled person, in particular radio base stations for wireless
communication.
[0065] In more detail, the second control node 108 or MSC (Mobile
Switching Centre, depicted in FIG. 1 as a Media Gateway Control
Function MGCF implemented in a Mobile Soft Switch MSS) knows
whether a particular subscriber is attached via SGs interface 114
or via another interface, for instance an A-, Iu-, or
Gs-interface.
[0066] Generally, only a Single Radio UE (SR UE) is attached as
user equipment 104 via SGs interface 114, not a Dual Radio (DR) UE
(Dual Radio UE do not use LTE and CSFB (Circuit Switch
Fallback)/SMSoSGs for voice or SMS, Short Message Service). DR UE
have both an LTE and a GSM receiver so that they may simultaneously
transmit data over LTE and voice over GSM. This allows operators to
omit the SGs interface 114 for simplification although it is also
possible in this case to have this interface.
[0067] The establishment and release of SGs associations over SGs
interface 114 may have different causes:
[0068] An SGs association is established from MME or third control
node 110 if SR UE or user equipment 104 performs EPC (Evolved
Packet Core)/IMSI (International Mobile Subscriber Identity) attach
or combined TA/LA (Tracking Area/Location Area) Update, for CSFB or
for SMS only, as specified in 3GPP TS 23.272
[0069] An SGs association is released, for instance, if:
[0070] the user equipment 104 performs LAU (Location Area Update)
via A-/Iu-/Gs-interface to the MSC or second control node 108
having the SGs association for this subscriber
[0071] the user equipment 104 performs LAU via A-/Iu-/Gs-interface
to another MSC and the MSC or second control node 108 having the
SGs association for this subscriber will receive a MAP (Mobile
Application Part) Cancel Location message
[0072] The MSC or second control node 108 can perform additional
checks to determine whether the subscriber is an IMS voice user,
for instance:
[0073] whether SRVCC (Single Radio Voice Call Continuity) is
enabled for this subscriber by checking STN (Session Transfer
Number)-SR or other "IMS Voice" indication via SGs (needs to be
provided by MME or third control node 110 to the MSC or second
control node 108 over the SGs interface 114, for instance at
establishment of the SGs association)
[0074] whether the subscriber is an ICS user by checking the ICS
indication (not shown in the call flow of FIG. 2; the ICS flag
needs to be provisioned in HLR as specified in 3GPP TS 23.292).
[0075] Such additional checks are not mandatory for any embodiment
but may improve the method in certain scenarios, for instance if
terminals without IMS voice capability are associated to the MSC or
second control node 108 via an SGs interface 114. For example, it
may be possible that some operators have such terminals with such a
property while other operators do not so that this option may for
instance improve the handling of roaming terminals.
[0076] When the GMSC (Gateway MSC) or first control node 106
receives a terminating call 102, it will send a message MAP (Mobile
Application Part) Send Routing Info (SRI) to the HLR 120, and the
HLR 120 will send MAP Provide Roaming Number message (PRN) to the
MSC or second control node 108 where the subscriber is registered,
for instance as in prior art systems. In an embodiment of the
invention, this MSC or second control node 108 returns for a
terminating call 102:
[0077] an MSRN if the subscriber has no SGs association, or if one
of the other conditions above are not fulfilled
[0078] an IMRN if the subscriber has an SGs association established
and all other conditions above are fulfilled
[0079] The IMRN can be a prefixed B number, i.e. a specific prefix
of the B number may identify it as an IMRN. Other IMRN options are
possible and may be selected depending on different administration
aspects. For example, a specific range of numbers may be defined as
IMRN.
[0080] Still referring to FIG. 1, HSS/HLR 122 performs update
location to HLR 120 and provides MSC ID of serving MSC or second
control node 108. Serving MSC or second control node 108 has a
logic to determine whether to route call to CS access or to IMS
112. So on receipt of PRN the MSC or second control node 108 acts
as follows:
[0081] if SGs is established, provide prefixed B-number (IMRN)
[0082] else provide MSRN
[0083] can take other input into account as well, if present
[0084] terminating SMS are handled by MSC via A/Iu or via SGs
[0085] In an embodiment, a specific logic in MSC needs only to be
supported by MSC supporting SGs (if user equipment 104 is attached
to other MSC then always terminate in CS). It is possible to use
SMSoSGs.
[0086] FIG. 2 below shows a call flow according to the
above-described method which may be used in the communication
system 100 as shown in FIG. 1.
[0087] Further network components are shown as well in the call
flow, i.e. P-CSCF (Proxy-Call Session Control Function) 200,
I/S-CSCF (Interrogation-/Serving-Call Session Control Function)
202, MTAS (Mobile terminating access service) 204, and a node B
208.
[0088] The GMSC or first control node 106 receives an IAM 1 for a
subscriber B and sends an SRI 2 to the HLR 120. If the
communication system 100 comprises both a legacy HLR 120 and an
HSS/HLR 122 adapted to IMS, the legacy HLR 120 may have obtained
the identification of the terminating MSC or second control node
108 in a prior procedure as indicated.
[0089] In FIG. 2, different roaming numbers are sent in the
alternative options for the response message 3. Depending on the
routing information provided, the IAM in step 4 is sent to
different target nodes and accordingly different terminating call
legs are set up as indicated in FIG. 1.
[0090] The call flow of FIG. 2 shows a "HSS/HLR 122" and a "HLR
120" which can be an "old HLR" for cases when the HSS/HLR 122 is
introduced when deploying LTE/EPC but the old HLR 120 is kept for
legacy call cases. The terminology new/old refers here to either an
HLR as used in CS systems or an HSS adapted to interworking with an
IMS system. However, the call flow is also applicable to cases
where only a "HSS/HLR 122" is present (i.e. the old HLR has been
replaced). The use of both "new HSS/HLR" and an "old HLR" and the
update location to the old HLR may be done as in conventional
systems.
[0091] FIG. 3 illustrates constitution of the second control node
108 of FIG. 1. The second control node 108 comprises a transmitter
interface 302 for sending data to a communicatively coupled node
and a receiver interface 304 for receiving data from a
communicatively coupled node. For instance, it is possible to
provide routing information at transmitter interface 302. A
processing system 306 (such as a microprocessor or a central
processing unit) is adapted to determine the association of the
user equipment 104 to the third control node 110 and for selecting
the routing information based on the determination. The second
control node 108 is further adapted to provide a routing
information which indicates that the user equipment 104 is
associated with the third control node 110. The second control node
108 further comprises a memory 308 accessible by the processing
system 306. Data, control parameter and/or software code for
operating the second control node 108 may be stored permanently or
temporarily on memory 308. Further components (not shown in FIG. 3)
may form part of the second control node 108 as well.
[0092] FIG. 4 illustrates constitution of the third control node
110 of FIG. 1. The third control node 110 comprises a transmitter
interface 402 for sending data to a communicatively coupled node
and a receiver interface 404 for receiving data from a
communicatively coupled node. For instance, it is possible to
provide information of the user equipment 104 attached to the third
control node 110 to a second control node 108 via transmitter
interface 402. A processing system 406 (such as a microprocessor or
a central processing unit) adapted to determine the association of
the user equipment 104 to the third control node 110 and
capabilities of the user equipment 104 to receive a call 102 under
the control of the third control node 110, and whether said user
equipment 104 is using or is adapted to use a specific service
domain 112 such as an IP Multimedia Subsystem. Data, control
parameter and/or software code for operating the third control node
110 may be stored permanently or temporarily on memory 408. Further
components (not shown in FIG. 4) may form part of the third control
node 110 as well.
[0093] FIG. 5 illustrates a flowchart of a method 500 of routing a
terminating call 102 to a user equipment 104 via a first control
node 106 for controlling the call 102 according to an exemplary
embodiment of the invention. The user equipment 104 is attached to
a second control node 108 which is adapted to provide routing
information (see reference numeral 502).
[0094] As can be taken from a block 504, the method 500 comprises
determining, by the second control node 108, if the user equipment
104 is attached to the second control node 108 over a third control
node 110, wherein the attachment over the third control node 110
indicates that call control shall be performed by a specific
service domain 112.
[0095] As can be taken from a block 506, based on the
determination, the provided routing information is selected 506 by
the second control node 108. The routing information indicates to
the first control node 106 if the further call establishment to the
user equipment 104 is controlled either by the second control node
108 or by the third control node 110.
[0096] As can be taken from a block 508, the call is then routed,
by the first control node 106, according to the selected routing
information.
[0097] It should be noted that the term "comprising" does not
exclude other elements or features and the "a" or "an" does not
exclude a plurality. Also elements described in association with
different embodiments may be combined.
[0098] It should also be noted that reference signs in the claims
shall not be construed as limiting the scope of the claims.
* * * * *